What is Distance

Distance is the actual length of the path travelled by the object.

 

What is Displacement

Displacement is shortest distance between initial and final position of the object.

Example 1

Distance from Delhi to Mumbai is 1500 km

Distance from Mumbai to Bangalore is 1000 km

Distance from Delhi to Bangalore is 2000 km

Suppose Sanjay goes from Delhi to Mumbai and then from Mumbai to Bangalore

Then what is the Distance and displacement travelled by him

 

In this Case

Distance Travelled = Distance from Delhi to Mumbai + Distance from Mumbai to Bangalore

= 1000 + 1500

= 2500km

        Displacement = Distance from Delhi to Bangalore

=2000 km

Note

Distance travelled by a moving object can never be 0

But Displacement can be 0

Example 2

Suppose a person travels from Delhi to Mumbai for 1500 km

Then he comes back from Mumbai to Delhi traveling another 1500 km

Distance Travelled = Distance from Delhi to Mumbai + Distance from Mumbai to Delhi

=1500 + 1500

= 3000 km

Displacement = 0

(as his Initial Position and Final Position is both Delhi)

 

Traveling in Circular Path

In this case,Distance can be calculated by using formula for Circumference of Circle

Circumference of Circle = 2 π R

However,Displacement will be 0 if an object completes the full round of the circle.

as on completion of circle,Initial and Final Position is Same.

 

Example 3

Suppose a person jogs in a park which is circular and completes one round

Diameter of Park is 20 meters

Then what is the Distance and displacement travelled by him

So Radius of Park is 20/2 = 10 m

 

Distance travelled = 2π×r

         = 2 × 22/7 × 10

         = 62.85

 

Displacement = Shortest distance between initial and final point

Since, initial point = final point, displacement = 0.

Note
Distance is a scalar quantity but Displacement is a Vector Quantity

Scalar Quantity means those quantities which have magnitude.

Vector Quantity means those quantities which have both magnitude and direction.

Example 4

Suppose a person travels from Kashmir to kanyakumari,he travels a distance of 3000 km towards south

Then what is the Distance and displacement travelled by him

In this case,

Distance = 3000 km

Displacement = 3000 Km towards south

 

Difference between Distance and Displacement 

Distance Displacement
Distance is the Actual length of the path travelled by the object.
Displacement is shorterest distance between initial and final position of the object.
It is a scalar quantity. It is a vector quantity.
Distance travelled by a body can never be zero. Displacement travelled by a body can be zero.
Distance can be positive or zero. Displacement can be positive, negative or zero.

 

How to Find Distance and Displacement if a person travels in Zig Zag Path?

Distance can be found by adding all length travelled

Displacement can be found by connecting starting and ending points with a straight line, the length of the string would give the displacement.

Zig zag path.png

Questions

Q 1 Page 100 - An object has moved through a distance. Can it have zero displacement? If yes, support your answer with an example.

View Answer

 

Q 2 Page 100 - A farmer moves along the boundary of a square field of side 10 m in 40 s. What will be the magnitude of displacement of the farmer at the end of 2 minutes 20 seconds from his initial position?

View Answer

 

Q 3 Page 100 - Which of the following is true for displacement?
(a) It cannot be zero.
(b) Its magnitude is greater than the distance travelled by the object

View Answer

 

NCERT Question 1 -   An athlete completes one round of a circular track of diameter 200 m in 40 s. What will be the distance covered and the displacement at the end of 2 minutes 20 s?

View Answer

  1. Class 9
  2. Chapter 8 Class 9 - Motion

About the Author

CA Maninder Singh's photo - Expert in Practical Accounts, Taxation and Efiling
CA Maninder Singh
CA Maninder Singh is a Chartered Accountant for the past 9 years and a teacher from the past 16 years. He teaches Spoken English, Written English, Grammar and Vocabulary at Englishtan.